BMS circuit design using BMS IC

20s BMS is a big deal. I am not sure about the Ah rating of each cell, its max charge and discharge current. So I cant tell you the exact IC part name. But If you want to start you have to look into Texas Instruments and Maxim because they has good support for BMS designs. You can start with the following links

http://www.ti.com/tool/TIDA-01093

https://www.maximintegrated.com/en/products/power/battery-management/MAX14920.html

Hope this helps 

A battery management system is any electronic system that manages a rechargeable battery such as by protecting the battery from operating outside its safe operating area monitoring its state, calculating secondary data, reporting that data, controlling its environment, authenticating it and / or balancing it.A battery pack built together with a battery management system with an external communication data bus is a smart battery pack. A smart battery pack must be charged by a smart battery charger.
   
Battery thermal management systems can be either passive or active, and the cooling medium can either be air, liquid, or some form of phase change. Air cooling is advantageous in its simplicity. Such systems can be passive, relying only on the convection of the surrounding air, or active, utilizing fans for airflow.The major disadvantage of air cooling is its inefficiency. Large amounts of power must used to operate the cooling mechanism, far more than active liquid cooling.The additional components of the cooling mechanism also add weight to the BMS, reducing the efficiency of batteries used for transportation.